activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.ramadan_apps.test.MainActivity">


    <com.ramadan_apps.mylibrary.CircleView
        android:id="@+id/circle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="121dp"
        android:layout_marginEnd="12dp"
        android:layout_marginStart="102dp"
        android:layout_marginTop="150dp"
        app:dim="100dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:shape="circle" />

</android.support.constraint.ConstraintLayout>